1. Field of the Invention
The present invention relates to telephone networks, and more particularly to a system and method for accessing, monitoring and testing a telephone network.
2. Description of the Related Technology
For some time, public switched telephone networks (PSTN) have utilized time division multiplexing (TDM) transmission systems to communicate both voice and data signals over a digital communications link. For example, digital signal level 1 (DS1), and more recently digital signal level 3 (DS3), data paths have long been used to carry both voice and data signals over a single transmission facility. DS1 data paths carry DS1 signals which are transmitted at a transmission rate of 1.544 Mbps, and DS3 data paths carry DS3 signals which are transmitted at a transmission rate of 44.736 Mbps. Consequently, both DS1 and DS3 data paths offer the advantage of considerably reducing the number of lines required to carry information that otherwise would be required without time division multiplexing the digital voice and data signals.
Nowadays, there are several regional Bell operating companies and independent telephone companies which provide local telephone service within numerous local access transport areas (LATA). These companies are forced to rely on interexchange carriers such as AT&T, MCI and Sprint for transmission of calls from one LATA to another. As a result, a long distance call or transmission from one end-user to another involves many levels of multiplexing and many transport carrier handoffs. The responsibility for quality and performance of the telephone circuit is thus split between local telephone companies and interexchange carriers.
Telephone companies often need an economical way to access circuits for testing and protocol analysis. Typically, each telephone company dispatches multiple repair crews with portable test equipment to a number of locations. The locations include the network boundary between the long distance and the local telephone company, the telephone building nearest the end-user, and to outside facilities such as the cables and equipment beneath streets and on poles between the central offices and the end-user customer. This method of maintenance results in significant inefficiencies. Hence, solutions which do not require dispatching repair crews with portable test equipment when problems occur were created. Today, telephone companies equipped with advanced systems can monitor circuits remotely from a network management center. However, with the split in responsibility among telephone companies comes significant difficulties in maintaining network circuits, troubleshooting and isolating transmission faults over their data paths: logical faults (which are protocol dependent) and physical faults (which are circuit dependent). Moreover, and perhaps more importantly, with data services and voice services sharing common networks, an organization maintaining a network common with another organization could easily access, interfere or disrupt circuit communications for the other organization.
Most network elements incorporate some form of monitoring, test, and control of the data that they process. However, none of these options supports the monitor-only function or restricted access (firewall) feature of the present invention. The U.S. Pat. No. 5,375,126 to Hekimian Laboratories, Inc., apparently describes a system which provides physical and protocol testing of digital data system (DDS). The Hekimian system, however, does not offer the firewall functionality of restricting or preventing a technician from accessing or interrupting unauthorized network circuits or other organization's equipment.
Thus, a restricted access method that provides continuous performance monitor-only of DS3 embedded channels and technician access restricted to authorized equipment are desired. It is desired to have a system which provides comprehensive, full-time performance monitoring-only of DS3 embedded channels (i.e. DS1, DS0 and subrate channels) through a digital cross-connect system (DCS) or directly connected circuits. It is further desired to provide a system having restricted circuit access (firewall feature) by data network technicians to ensure that a network organization accesses only its own equipment or authorized facilities. With the restricted access feature, other organizations will no longer have to be concerned about unauthorized access to their circuits nor about interference or interruption caused by unauthorized access by data network technicians. In addition, it is also desired to provide testing of DS1, DS0 and subrate circuits, along with an extensive suite of test capabilities for HiCap, DDS and VF services only for authorized or core network technicians.